Dual cutting mill

Abstract

A rotating tool for milling or drilling in a well bore, having one or more rotating cutting structures, with each cutting structure rotating about its own axis, and with the cutting structures rotating about the axis of the tool. The rotational axis of the tool is offset from the axis of at least one cutting structure, with the axis of the tool passing through that cutting structure. This ensures that the cutting structure which spans the axis of the tool rotates independently of the tool, to prevent the existence of a zero velocity point on the cutting face of the tool.

We claim:  
     
       1. A tool for removing downhole material from a well bore, comprising: 
       a cutting structure adapted for connection to a lower end of a drill string for positioning in the well bore, said cutting structure being rotatable about its longitudinal axis;  
       wherein said cutting structure is also rotatable about the longitudinal axis of said tool;  
       wherein said longitudinal axis of said cutting structure is parallel to, but laterally offset from, said longitudinal axis of said tool; and  
       wherein said longitudinal axis of said tool passes through said cutting structure;  
       a housing connectable to the lower end of the drill string for rotation;  
       means drivably connecting the drill string to said housing for rotating said housing; and  
       a drill motor mounted within said rotatable housing;  
       wherein said cutting structure is rotatably mounted to a lower end of said rotatable housing, said cutting structure being drivably engaged by said drill motor.  
     
     
       2. A tool as recited in  claim 1 , wherein said means drivably connecting the drill string to said housing fixedly attaches said housing to the drill string for rotation by rotation of the drill string. 
     
     
       3. A tool for removing downhole material from a well bore, comprising: 
       a cutting assembly adapted for connection to a lower end of a drill string for positioning in the well bore, said cutting assembly being rotatable about its longitudinal axis, said cutting assembly including first and second cutting structures, each said cutting structure being adapted for rotation about its respective longitudinal axis, at least one of said first and second cutting structures being adapted for rotation by at least one drill motor mounted for rotation with said cutting assembly;  
       a housing connected to the drill string, said cutting assembly being mounted to said housing; and  
       means drivably connecting the drill string to said housing for rotating said housing;  
       wherein said first and second cutting structures, in combination. extend substantially across the diameter of a louver end of said cutting assembly;  
       wherein said longitudinal axis of said second cutting structure is parallel to, but laterally offset from, said longitudinal axis of said cutting assembly; and  
       wherein said longitudinal axis of said cutting assembly passes through said second cutting structure.  
     
     
       4. A tool as recited in  claim 3 , wherein: 
       said first cutting structure is fixedly mounted to said lower end of said rotatable housing; and  
       said second cutting structure is rotatably mounted to said lower end of said rotatable housing, said second cutting structure being drivably engaged by said at least one drill motor.  
     
     
       5. A tool as recited in  claim 4 , wherein said means drivably connecting the drill string to said housing fixedly attaches said housing to the drill string for rotation by rotation of the drill string. 
     
     
       6. A tool as recited in  claim 3 , wherein: 
       said first cutting structure is drivably engaged by said at least one drill motor for rotation about its longitudinal axis; and  
       said second cutting structure is drivably engaged by said at least one drill motor for rotation about its longitudinal axis.  
     
     
       7. A tool as recited in  claim 6 , wherein said at least one drill motor is fixedly attached to the drill string for rotation by rotation of the drill string. 
     
     
       8. A tool as recited in  claim 6 , further comprising a single input, dual output drive member for driving said first and second cutting structures with said at least one drill motor. 
     
     
       9. A tool for removing downhole material from a well bore, comprising: 
       a housing adapted for connection to a lower end of a work string for positioning in the well bore, said housing being rotatable about its longitudinal axis;  
       means on the work string for drivably rotating said housing;  
       a cutting assembly mounted to a lower end of said housing, said cutting assembly including first and second cutting structures, said first cutting structure being fixed mounted to said lower end of said rotatable housing, said second cutting structure being rotatable about its longitudinal axis relative to said housing; and  
       a drill motor fixedly mounted within said rotatable housing, said second cutting structure being drivably engaged by said drill motor for rotation relative to said housing;  
       wherein said first and second cutting structures, in combination. extend substantially across the diameter of said cutting assembly;  
       wherein said longitudinal axis of said second cutting structure is parallel to, but laterally offset from, said longitudinal axis of said housing; and  
       wherein said longitudinal axis of said housing passes through said second cutting structure.  
     
     
       10. A tool as recited in  claim 9 , wherein said means for drivably rotating fixedly attaches said housing to the work string for rotation by rotation of the work string.